Epicyclic gear train is used in various power train applications for transferring rotary power from an input to an output while changing speed to the output. The most popular use of epicyclic gear train is for planetary gears in automatic vehicles' transmissions. Conventional epicyclic gear train consists of spur or helical gears. Example of different designs of epicyclic gear train is described in U.S. Pat. No. 1,998,891 by Benson, U.S. Pat. No. 2,441,989 by Brown, U.S. Pat. No. 3,934,493 by Hillyer, U.S. Pat. No. 4,043,216 by Steer, U.S. Pat. No. 6,042,086 by Roberts and many patents with planetary gear transmissions.
Examples of using right angle face gears in epicyclic gear train are published in U.S. Pat. No. 6,183,388 by Hawkins, U.S. Pat. No. 2,313,183 by Trbojevich and U.S. Pat. No. 2,924,998 by Sem.
Enveloping worm gearsets, otherwise referred to as enveloping worm/worm gear transmissions, are known in the mechanical power transmission field. The worm gear is driven by the rotation of the enveloping worm with which it meshes. The rotational speed of the associated shaft of the worm gear is a function of the number of teeth on the worm gear and the number of threads on the enveloping worm. The enveloping worm may be single or multiple threaded. The most known enveloping worm is from U.S. Pat. No. 1,683,163 by Cone. Enveloping worm usually has 360 degree or more of thread revolution and is in mesh with matting worm gear where it is placed on top of the worm gear. Axis of rotation of enveloping worm and axis of rotation matting gear are crossed. They are not intersected. This type of mesh has sliding motion along gear tooth and some percentage of rolling motion around axis of worm gear rotation that produces low efficiency reduction and is not recommended to be used in power transferring of mechanical motion. Epicyclic gear train with enveloping worm/worm gear transmission is used as a differential. In U.S. Pat. No. 4,890,511 by Pedersen first enveloping worm satellite is in meshing engagement with first matting gear and second, exactly the same, enveloping worm satellite is in meshing engagement with second matting gear. To produce differential motion it has additional gears for kinematical connection of first enveloping worm satellite with second enveloping worm satellite. The enveloping worm satellites are not attached to each other. Due to low efficiency this epicyclic gear train is used only occasionally for correction of traction.